Solution-processable nickel–chromium ternary oxide as an efficient hole transport layer for inverted planar perovskite solar cells

Abstract

Organic–inorganic hybrid perovskite solar cells (PSCs) have shown advantages of high efficiency, solution production, and flexibility, and have become a potential candidate for next-generation photovoltaic technologies. For PSCs in p–i–n configuration, inorganic p-type semiconductors are competitive as hole transport layers (HTLs) due to their low-cost, chemical stability, high transparency, and solution processability. Herein, solution-processed, ternary metal oxide NiCrO₃ films were reported as HTLs in PSCs. Compared with the most prevalent NiO_x HTLs, the uniform and pin-hole free NiCrO₃ HTLs delivered higher electrical conductivity and a deeper valence band, enabling improved hole transport and interfacial band alignment. The NiCrO₃ HTLs also present accelerated charge extraction and slow charge recombination as observed by transient spectroscopy studies. A high power conversion efficiency (PCE) of 19.93% was achieved, which is much higher than that of a NiO_x based device (18.35%). This work demonstrated the potential of NiCrO₃ as an effective HTL in PSCs, and may promote the development of ternary metal oxides as new building blocks for high performance PSCs.